In a conventional mobile communication system, in an uplink from a mobile station UE to a radio bass station Node B, a radio network controller RNC is configured to determine a transmission rate of a dedicated channel, in consideration of radio resources of the radio base station NodeB, an interference volume in an uplink, transmission power of the mobile station UE, transmission processing performance of the mobile station UE, a transmission rate required for an upper application, and the like, and to notify the determined transmission rate of the dedicated channel by a message of a layer-3 (Radio Resource Control Layer) to both of the mobile station UE and the radio base station Node B.
Here, the radio network controller RNC is provided at an upper level of the radio base station Node B, and is an apparatus configured to control the radio base station Node B and the mobile station UE.
In general, data communications often cause burst traffic compared with voice communications or TV communications. Therefore, it is preferable that a transmission rate of a channel used for the data communications is changed fast.
However, as shown in FIG. 10, the radio network controller RNC integrally controls a plurality of radio base stations Node B in general. Therefore, in the conventional mobile communication system, there has been a problem that it is difficult to perform fast control for changing of the transmission rate of channel (for example, per approximately 1 through 100 ms), due to processing load, processing delay, or the like.
In addition, in the conventional mobile communication system, there has been also a problem that costs for implementing an apparatus and for operating a network are substantially increased even if the fast control for changing of the transmission rate of the channel can be performed.
Therefore, in the conventional mobile communication system, control for changing of the transmission rate of the channel is generally performed on the order from a few hundred ms to a few seconds.
Accordingly, in the conventional mobile communication system, when burst data transmission is performed as shown in FIG. 11(a), the data are transmitted by accepting low-speed, high-delay, and low-transmission efficiency as shown in FIG. 11(b), or, as shown in FIG. 11(c), by reserving radio resources for high-speed communications to accept that radio bandwidth resources in an unoccupied state and hardware resources in the radio base station Node B are wasted.
It should be noted that both of the above-described radio bandwidth resources and hardware resources are applied to the vertical radio resources in FIG. 11.
Therefore, the 3rd Generation Partnership Project (3GPP) and the 3rd Generation Partnership Project 2 (3GPP2), which are international standardization organizations of the third generation mobile communication system, have discussed a method for controlling radio resources at high speed in a layer-1 and a media access control (MAC) sub-layer (a layer-2) between the radio base station Node B and the mobile station UE, so as to utilize the radio resources effectively. Such discussions or discussed functions will be hereinafter referred to as “Enhanced Uplink (EUL)”.
Conventionally, the following two types of transmission rate control method have been known as transmission rate control methods in “EUL”. (refer to the Non-patent document 1) Hereinafter, the transmission rate control method will be described in detail.
Firstly, a transmission control method called “RG mode” has been known. “RG mode” is mainly used for a case where a transmission rate of uplink user data is dedicatedly controlled.
It should be noted that “RG mode” is a mode which controls a transmission rate of uplink user by using an absolute transmission rate control channel for notifying absolute value of a transmission rate of uplink user data (or a parameter related to the transmission rate), and a relative transmission rate channel for notifying relative value (Up/Down/Hold) of a transmission rate of uplink user data (or a parameter related to the transmission rate).
Specifically, as shown in FIG. 13, a mobile station UE is configured to receive absolute value of a transmission rate of uplink user data (or a parameter related to the transmission rate) via an E-AGCH (E-DCH Absolute Grant Channel: Absolute Transmission Rate Control Channel) transmitted from cell #21 of a radio base station Node #2. The cell #21 is a serving cell of the mobile station UE.
Further, as shown in FIG. 13, the mobile station UE is configured to receive relative value of a transmission rate of uplink user data (or a parameter related to the transmission rate) via an E-RGCH (E-DCH Relative Grant Channel: Relative Transmission Rate Control Channel) transmitted from cell # 13 of radio base station Node #1, cell #21 of the radio base station Node B #2, and cell #22 of the radio base station Node B#2. Here, the cell #13 is a non-serving cell of the mobile station UE, the cell #21 is a serving cell of the mobile station UE, and the cell # 22 is a cell belonging to a serving cell set of the mobile station UE.
Generally, unless specified otherwise, the E-RGCH, which is transmitted from the radio base station Node B, indicates any of the E-RGCH transmitted from a serving cell of the radio base station Node B, the E-RGCH transmitted from a cell belonging to a serving cell set, or the E-RGCH transmitted from a non-serving cell. Further, the E-AGCH, which is transmitted from the radio base station Node B, indicates an E-AGCH transmitted from a serving cell of the radio base station Node B.
In “RG mode”, the E-RGCH transmitted from the radio base station Node B (specifically, a serving cell of the radio base station Node B, a cell belonging to the serving cell set or a non-serving cell) is a dedicated transmission rate control channel, which is different for each mobile station UE. Further, the E-AGCH transmitted from the radio base station Node B (specifically, a serving cell of the radio base station Node B) is a dedicated transmission rate control channel, which is different for each mobile station UE.
It should be noted that there is a case where E-AGCH is simply referred to as “AGCH (Absolute Grant Channel)” and E-RGCH is simply referred to as “RGCH (Relative Grant Channel)”.
Secondly, a transmission control method called “Non-RG mode” or “Autonomous ramping” has been known. “Autonomous ramping” is used when controlling a transmission rate of uplink user data commonly for the mobile stations in the cell.
According to “autonomous ramping”, a radio base station Node B notifies an E-AGCH (E-AGCH of FIG. 18 and common transmission rate control channel), which is common for the cells, to mobile station UE, and each of the mobile station UE increases a transmission rate of uplink user data (or a parameter related to the transmission rate of uplink user data) by predetermined steps, from an initial transmission rate (or a parameter related to the initial transmission rate) included in the E-AGCH, up to a maximum allowable transmission rate (or a parameter related to the maximum allowable transmission rate) included in the E-AGCH.
It should be noted that in “Autonomous ramping”, each of the mobile station UE is configured to increase the transmission rate of uplink user data up to the maximum allowable transmission rate by predetermined steps. Accordingly, both of the following case can be assumed; a case in which the transmission rate of uplink user data is increased up to the maximum allowable transmission rate by taking a predetermined number of steps; or a case in which the transmission rate of uplink user data is increased up to the maximum allowable rate by taking only one step.
Further, in the EUL, “Scheduled transmission” and “Non-scheduled transmission” is defined.
In “scheduled transmission”, a mobile station UE is configured to control a transmission rate of uplink user data based on a transmission rate control channel (absolute transmission rate control channel or relative transmission rate control channel) transmitted from the radio base station Node B. (refer to FIG. 12)
To be more specific, in “scheduled transmission”, the mobile station UE is configured to control the transmission rate of uplink user data based on the E-AGCH (absolute transmission rate control channel) and the E-RGCH (relative transmission rate control channel) shown in FIG. 13.
Further, in “non-scheduled transmission”, the mobile station UE is configured to, when not receiving the above-described transmission rate control channel, determine the transmission rate of uplink user data for each logical channel or upper data flow within the allowable maximum transmission rate determined by a radio network controller RNC (refer to FIG. 12).
However, in the non-scheduled transmission, the mobile station UE cannot use other than a fixed transmission rate for the transmission rate of uplink user data. Therefore, there has been a problem that the transmission rate of uplink user data has to be set as “high-speed” for a channel in which high-speed response is required.
The present invention has been made considering the above-described problems, and its object is to provide a transmission rate control method and a mobile station that makes it possible to satisfy required quality of communication (QoS) in each channel and to improve a radio quality, by applying “Autonomous ramping” and enabling automatic increase of a transmission rate of uplink user data in the non-scheduled transmission, and by dedicatedly controlling a transmission rate of uplink user data in the scheduled transmission.
(Non-patent Document 1) 3GPP TSG-RAN TS-25.309 v6.1.0